1. Field of the Invention
This invention relates to pump control systems and especially to such systems designed for use in maintaining a constant flow through the wet well of a sewage treatment facility.
2. Discussion of Related Art
Wet wells and settling tanks are commonly used in sewage treatment plants for allowing solids to settle out of the effluent or waste water being treated. It is a well known fact that the most efficient sewage system is one that is gravity fed. When a plant is pulsed by pumps working on and off by float switches, it riles the water and retards the settling of solids, while a constant flow aids settling. Accordingly, it is desirable to maintain proper wet well level by controlling flow from the wet well in response to the gravity fed flow into the wet well.
Various systems have been devised for pump controls. For instance, U.S. Pat. No. 3,937,596, issued Feb. 10, 1976 to Braidwood, shows a fluid pump drive control for a variable speed motor which control utilizes a bubbler tube to provide an accurate indication of the fluid in the wet well. U.S. Pat. No. 3,741,683, issued June 26, 1973 to McTamaney, shows a liquid level control system which uses a plurality of sequentially actuated motors for controlling the rate of flow from a tank. U.S. Pat. No. 3,393,642, issued July 23, 1968 to Kordik, shows an adjustable speed pumping system which uses a bubbler tube for providing an indication of fluid height in a wet well. U.S. Pat. No. 3,463,981, issued Apr. 26, 1969 to Wires, shows a control system for bidirectional electrical motors which are operable as a drive and overdrive for a followup mechanism having utility as part of a motored monometer for indicating and recording fluid level variations. Use is made of a liquid level detector arrangement including a linear differential transformer having a float actuated armature which provides directive signals to a motor controlled circuitry.
While the above cited devices operate effectively, none produces the smooth, controlled operation necessary to insure the most efficient settling of solids from sewage effluent.